It is very important to train the trunk and the muscles surrounding the area from the pelvis to the hip joint for the purpose of strengthening the trunk and enhancing the stability thereof, increasing an abdominal pressure to slim down (reduce the size of) the area around the waist, and adjusting posture. In order to achieve this purpose, some training apparatus and training methods using the training apparatus have been proposed. For example, there are a method involving causing a person who performs muscle training to sit on a seat of the training apparatus, with the pelvis being fixed so as not to move, and causing the person to rotate the shoulders and the chest to twist the upper body, and a training apparatus and method involving causing a person who performs muscle training to sit on a rotatable seat, with the shoulders and the chest being fixed so as not to move, and causing the person to rotate the seat to twist the waist.
The above-mentioned apparatus and methods are all effective for training the trunk, in particular, the external abdominal oblique muscle and the internal abdominal oblique muscle, but are not so effective for training the entire trunk and the muscles surrounding the area from the pelvis to the hip joint.